/Engine/Plugins/Runtime/nDisplay/Source/DisplayClusterMedia/Public/Synchronization/DisplayClusterMediaOutputSynchronizationPolicyThresholdBase.h
Basically it uses the same approach that we use in 'Ethernet' sync policy where v-blanks are used as the timepoints.
[UCLASS](Programming/UnrealArchitecture/Reference/Classes#classdeclaration)(Abstract, EditInlineNew, BlueprintType, HideCategories=(Object)) class UDisplayClusterMediaOutputSynchronizationPolicyThresholdBase : public [UDisplayClusterMediaOutputSynchronizationPolicyEthernetBarrierBase](API\Plugins\DisplayClusterMedia\Synchronization\UDisplayClusterM-_1)
int32
MarginMs
Synchronization margin (ms)